While carpets are generally manufactured by a number of methods, processes such as tufting and needle punching have become quite popular in the last few years. In particular, the majority of carpeting manufactured today is produced by the tufting process. Such tufted carpets have been manufactured for a number of years, and generally comprise composite structures in which tufts, or bundles of carpet fibers are introduced (such as by stitching) into a primary backing or scrim, such as a woven or non-woven fabric. A secondary backing or coating of thermoplastic material is then applied to the underside of the carpet construction in order to securely retain the tufted material in the primary backing. This secondary backing not only dimensionally stabilizes this construction but also provides greater abrasion and wear resistance, and serves as the adhesive for the barrier coating.
Many materials have been employed as the primary base or backing, and these preferably include woven materials such as jute, polypropylene film, etc. The primary backing can also comprise a non-woven fabric such as needle punched, non-woven polypropylene web, etc. For many years, the aqueous latex method has been employed for the secondary backing materials, but in recent years a hot melt adhesive composition has been utilized for such secondary carpet backing purposes. These have included thermoplastic resinous materials, such as powdered polyethylene.
Another commercially important carpet manufacturing process is needle punching. In this process the carpet fibers are punched by a series of barbed needles which causes them to mechanically interlock and form a non-woven loose fabric structure. In both of these above-described commercial processes the problem of fiber loss is always present. It has thus been necessary to employ a back coating in both cases, for this reason and also to provide such dimensional stability and body thereto. The problem of such fiber loss is particularly acute in connection with automotive carpeting where wear is generally concentrated into limited areas and the carpet is subjected to sliding and other forces which have resulted in excessive fiber loss therein.
As an improvement over the previously used powdered polyethylene coating as the secondary carpet backing, and in an attempt to provide a sound and thermal barrier in connection with automotive carpeting, attempts have been made to apply various thermoplastic resin layers to the carpeting. U.S. Pat. No. 3,525,662, for example, teaches the use of a coating of thermoplastic material comprising a mixture of polyolefin and low viscosity saturated hydrocarbon such as petroleum wax. The patentee claims that this inclusion of low viscosity material increases the speed of processing as well as the wear characteristics of his final carpet product, which is said to be particularly intended for use in automotive carpeting.
Subsequently, Collins and Aikman Corporation developed a calcium carbonate-loaded ethylene/vinyl acetate copolymer system which had many desirable properties for use in such systems. U.S. Pat. No. 3,551,231 discloses the application of a hot melt adhesive blend of ethylene/vinyl ester copolymer, petroleum wax, and a thermoplastic resin, in this case in conjunction with the application of a critical degree of pressure on the tufted structure during contact with the adhesive applicator roll.
Further developments in connection with secondary carpet backings includes that in U.S. Pat. No. 3,390,035, which discloses the use of a molten thermoplastic adhesive material including an ethylene/vinyl acetate copolymer, wax, and optionally a thermoplastic resin other than the ethylene copolymer.
In U.S. Pat. No. 3,684,600 a low viscosity precoated adhesive is disclosed for application to the back side of a tufted carpet structure prior to the application of the hot melt adhesive. The back side adhesive disclosed in that patent again contains ethylene/vinyl ester copolymer, in this case along with low molecular weight, low density polyethylene, microcrystalline wax, aliphatic thermoplastic hydrocarbon resin, dicyclopentadiene alkylation polymer, antioxidant, and filler.
Similar such compositions are disclosed in U.S. Pat. Nos. 3,583,936 and 3,745,054, and improvements on these compositions are alleged to be included in U.S. Pat. No. 3,914,489 which discloses such carpet backings including ethylene/vinyl ester copolymer, a hydrocarbon resin having a prescribed softening point and viscosity, and optionally also low molecular weight ethylene homopolymer, paraffin wax, antioxidant, and filler.
U.S. Pat. No. 3,982,051 discloses yet another backsizing carpet hot melt composition, in this case including ethylene/vinyl acetate copolymer, atactic polypropylene, and vulcanized rubber.
In general, aside from these thermoplastic resin systems, the commercial systems developed for such carpet backings include the above referred-to latex system, as well as vinyl and urethane based compositions.
Furthermore, it has also been known in the past to employ various combinations of ethylene copolymer elastomers with other copolymers of ethylene for use in different environments from that of the present invention. For example, U.S. Pat. No. 3,821,333 discloses the use of a mixture of ethylene/vinyl acetate copolymer with terpolymers of ethylene, propylene and a conjugated diene (EPDM). In this particular patent, the mixture is used as a gasket for lens molds. Furthermore, U.S. Pat. No. 4,046,840 discloses blends of EPDM polymers and polyethylene for use to prepare molded products, tubing etc.; U.S. Pat. No. 4,131,564 discloses blends of EPDM polymer, ethylene/ethyl acrylate polymer and optionally polyethylene, in this patent for the preparation of tube and sheet products, wire and cable insulation and the like; and British Pat. No. 1,524,986 discloses polymer blends of EPDM with ethylene/vinyl acetate copolymer.
The search has continued, however, for improved compositions for use in the preparation of automotive carpet backing.